Recently, remarkable progress has been made in the semiconductor industry, such as of LSI, and ultra LSI, and integration in semiconductor elements has been rushed into an era of megabit. Thus, fine processing of the order of submicron is being demanded.
In production of such semiconductor elements, so-called lithographic techniques are generally used, which comprise providing a photoresist layer on a substrate, such as a silicon wafer, then irradiating the photo resist layer, with an actinic ray, through a photo mask or lith film provided thereon with a pattern of the desired shape, and thereafter subjecting the layer to development treatment and etching treatment to form the pattern on the silicon wafer substrate or printed circuit.
Photo resists include two types; the negative type in which only the portion exposed to actinic ray is cured and the unexposed portion is dissolved out upon development; and the positive type in which only the portion exposed to actinic ray is dissolved out upon development, which is directly opposite to the negative type.
Generally, a protective film, for prevention of damage to the pattern and to impart durability, is used over the materials used for forming the pattern, such as a photo mask and lith film.
As a lith film provided with a protective film, there is known one which comprises a material such as a polyester film, provided with a pattern of the desired shape, on which is laminated an organic film, such as a polyester, through an adhesive.
However, such lith films having a protective film are inferior in durability because the protective film per se is readily marred. Besides, since the thickness of the film is about 10-20 .mu.m, when actinic rays are irradiated onto the photoresist layer through this lith film, deflection and scattering of the actinic ray can cause changes in the line width of the pattern and reduction in resolution. There are also photo masks and lith films free from lamination, but in this case, the pattern is uncovered and is readily subject to damage due to wear in operation.
The object of the present invention is to provide a pattern forming material having superior durability which is free from the defects of the conventional pattern forming material, such as photo mask and lith film provided with protective film, and which is provided with a protective film, which is excellent in mechanical, chemical and optical properties, by simple means without causing a reduction in resolution.